Time conversion

Frames and seconds are two spellings of the same clock: the comp's frame grid is canonical, and these helpers convert between the two without accumulating float error.

timeToFrames#

timeToFrames(t?: number, fps?: number): number

Seconds to a floored frame count (the comp fps by default).

Determinism: pure.

After Effects equivalent: timeToFrames.

Worked example: A frame mark from seconds#

The scene. One orange square resting on a dark 640 by 360 stage.

• The comp Drift: 640 by 360 at 25 fps, 100 frames (4 seconds).
• Square: a solid layer, at [320, 180], 60 by 60, filled #f2a833.

The script. Add a project script named Two second mark and paste:

export const outputs = ["layer_1:transform.opacity"];

export function frame({ frame }) {
  const mark = timeToFrames(2);
  return frame >= mark ? 40 : 100;
}

Line by line:

• Line 4: timeToFrames() turns seconds into a frame count on the comp's grid (rounded down) - at 25 fps, two seconds is frame 50. Write the intent in seconds and let the helper find the frame.
• Line 5: Before the mark the Square is solid; from frame 50 on it dims to 40.

What you see. The square holds full strength for exactly two seconds, then steps down to 40 percent for the rest of the comp.

framesToTime#

framesToTime(f: number, fps?: number): number

A frame count to seconds (the comp fps by default).

Determinism: pure.

After Effects equivalent: framesToTime.

Worked example: Hold, then go#

The scene. One orange square resting on a dark 640 by 360 stage.

• The comp Drift: 640 by 360 at 25 fps, 100 frames (4 seconds).
• Square: a solid layer, at [320, 180], 60 by 60, filled #f2a833.

The script. Add a project script named Delayed start and paste:

export const outputs = ["layer_1:transform.position"];

export function frame() {
  const start = framesToTime(50);
  return [value[0] + Math.max(0, time - start) * 60, value[1]];
}

Line by line:

• Line 4: framesToTime() is the other direction: frame 50 on this comp's grid is 2.0 seconds. Author the cue in frames, do the maths in seconds.
• Line 5: Math.max holds the offset at zero until the start time passes, then the Square slides right at 60 pixels per second.

What you see. The square sits still for two seconds, then sets off rightwards at a steady 60 pixels per second.